From owner-freebsd-hackers Sun Nov 10 13:53:20 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id BC6C237B401 for ; Sun, 10 Nov 2002 13:53:19 -0800 (PST) Received: from mail.sandvine.com (sandvine.com [199.243.201.138]) by mx1.FreeBSD.org (Postfix) with ESMTP id 38B4343E75 for ; Sun, 10 Nov 2002 13:53:19 -0800 (PST) (envelope-from don@sandvine.com) Received: by mail.sandvine.com with Internet Mail Service (5.5.2653.19) id <42S9V9GG>; Sun, 10 Nov 2002 16:53:18 -0500 Message-ID: From: Don Bowman To: "'freebsd-hackers@freebsd.org'" Subject: stack alignment, XEON / P4 Date: Sun, 10 Nov 2002 16:53:17 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain; charset="iso-8859-1" Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG In sys/conf/kern.mk, there is a comment about not aligning the (x86) stack to 16-byte boundaries, and it overrides the preferred-stack-boundary to 2. .if ${MACHINE_ARCH} == "i386" CFLAGS+= -mno-align-long-strings -mpreferred-stack-boundary=2 .endif This seems to be contradicted by intel's optimisation guide for the P4/XEON family. It seems that the performance is best by making it 4, even for older chips. Is there any hidden pitfall to changing this value? I compiled a kernel, and all seems to run ok. --don (don@sandvine.com www.sandvine.com) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message